If it still has the original TV instead of the newer flat screens units, it is probably quite heavy and it is subject to movement while in motion. Are you sure that it is the TV that is moving and not the cabinet that it is mounted in? Sometimes the cabinets can get loose and will rub against adjacent cabinets and cause a squeaking noise.
I have changed out three TV's in coaches that I have had and I am not sure that there were any "standard" way that they were attached in the cabinet. I doubt if you only had two screws holding the TV. There are probably several more that might have to be accessed from the side, top, or bottom. If there is a cabinet "face" around the screen, it may have to be removed for better access.